Instruments and techniques for separating bony structures

ABSTRACT

Instruments and techniques separate or spread adjacent bony structures by inserting a distal spreader assembly into the space between the adjacent bony structures and actuating the spreading members with a proximal actuator assembly.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/441,689 filed May 20, 2003 now U.S. Pat. No. 7,749,231, which claimsthe benefit of the filing date of U.S. Provisional Application Ser. No.60/382,408 filed on May 21, 2002 and also claims the benefit of thefiling date of U.S. Provisional Application No. 60/411,562 filed on Sep.18, 2002. The referenced applications are incorporated herein byreference in their entirety.

BACKGROUND

Adjacent bony structures can require separation for appropriatetreatment or repositioning of the bony structures. Separating the bonystructures can facilitate insertion of instruments and implants into thespace between bony structures.

For example, the spinal disc space between adjacent vertebrae cancollapse completely or partially, causing pain and trauma for theafflicted person. Other conditions associated with the spinal column canalso require access to a spinal disc space for appropriate treatment.Surgical techniques for treating such conditions can require theadjacent vertebrae to be distracted or spread apart to restore orpartially restore the spacing, or to increase the spacing, between theadjacent vertebrae.

There remain various needs for instruments and techniques that can beemployed for separating bony structures. The present invention isdirected to meeting these needs, among others.

SUMMARY

The invention relates to instruments and techniques for separatingadjacent bony structures.

According to one aspect, a spreader instrument is provided that includesa distal spreader assembly for insertion in the space between bonystructures and a proximal actuator assembly for actuating the spreaderassembly to separate the bony structures.

According to another aspect, a spreader instrument is provided thatincludes a distal spreader assembly for insertion in the space betweenbony structures and a proximal actuator assembly for actuating thespreader assembly to separate the bony structures. The distal spreaderassembly includes opposite bony structure contacting surfaces, at leastone of which includes an etched bone contacting surface.

According to a further aspect, a spreader instrument is provided thatincludes a distal spreader assembly for insertion in the space betweenbony structures and a proximal actuator assembly for actuating thespreader assembly to separate the bony structures. The spreader assemblyincludes opposite surfaces for contacting bony structures. The oppositesurfaces each include bone engaging features for engaging the adjacentbony structure to maintain the spreader assembly in contact therewith.Bone engaging features may include any one or combination of pitting,knurling, serrations, teeth, ridges, barbs, spikes, peeks and valleys,grooves, concave curvature, and convex curvature.

According to another aspect, a spreader instrument is provided thatincludes a distal spreader assembly for insertion in the space betweenbony structures and a proximal actuator assembly for actuating thespreader assembly to separate the bony structures. The spreader assemblyincludes first and second spreading members that are positionableadjacent one another in a low profile configuration for insertion intothe space between the bony structures and thereafter movable away fromone another to contact respective ones of the adjacent bony structuresto separate the bony structures. The low profile arrangement caninclude, for example, nesting the spreading members, collapsing of thespreading members, overlapping the spreading members, and/or compressingthe spreading members.

According to a further aspect, a spreader instrument is provided thatincludes a distal spreader assembly for insertion in the space betweenbony structures and a proximal actuator assembly for actuating thespreader assembly to separate the bony structures. The spreader assemblyincludes spreading members having opposite surfaces for contacting thebony structure. The spreading members are engaged to the actuatorassembly so that the spreading members remain parallel to one another asthe spreading members are moved away from one another to spread theadjacent bony structure. The engagement of each of the spreading membersto the actuator assembly can include a fastener movably received in aslot so that a connection location between the actuator assembly and therespective spreading member is variable within the slot.

According to a further aspect, a spreader instrument is provided thatincludes a distal spreader assembly for insertion in the space betweenbony structures and a proximal actuator assembly for actuating thespreader assembly to separate the bony structures. The spreader assemblyincludes opposite spreading members for contacting the bony structure.The spreading members each have a length sufficient to extend in thespace across a substantial portion of the adjacent bony structures. Thespreading members each have a cross-sectional modulus or moment ofinertia that limits deflection of the spreading member within anacceptable range when the spreading member applies a separating force tothe adjacent bony structure.

In another aspect of the invention, a spreader instrument is providedwith spreading members for contacting bony structures. Thecross-sections of the spreading members provide a low profileconfiguration when the spreading members are positioned adjacent oneanother for insertion of the spreading members into the space betweenthe adjacent bony structures. The length to depth ratio of the spreadingmembers can also be sufficient to provide adequate resistance to bendingof the spreading members.

According to another aspect, a method for separating adjacent vertebraeis provided. Spreading members are inserted into an at least partiallycollapsed disc space between the adjacent vertebrae. The spreadingmembers are actuated to spread the adjacent vertebrae. The spreadingmembers have a length sufficient to spread or distract the entire depthof the disc space between the vertebrae. Instruments are inserted intothe disc space to perform surgical procedures while the spreadingmembers maintain separation of the vertebrae. One or more implants canalso be inserted in the disc space while the spreading members maintainseparation of the adjacent vertebrae.

According to one aspect, a spreader instrument is provided that includesa distal spreader assembly for insertion in the space between bonystructures and a proximal actuator assembly for actuating the spreaderassembly to separate the bony structures. The distal spreader assemblyincludes a pair of spreading members each having at least one supportsurface extending therealong adapted to guide a cutting instrument in aspinal disc space.

According to a further aspect, a spreader instrument is provided thatincludes a distal spreader assembly for insertion in the space betweenbony structures and a proximal actuator assembly for actuating thespreader assembly to separate the bony structures. The distal spreaderassembly includes a pair of spreading members each having a guidemember. Disc space preparation, implants, and/or implant insertioninstruments can be guided into the disc space between the guide members.

According to one aspect, a spreader instrument is provided that includesa distal spreader assembly for insertion in the space between bonystructures and a proximal actuator assembly for actuating the spreaderassembly to separate the bony structures. The distal spreader assemblyincludes a pair of spreading members each having a pair of distalextension members positionable in the spinal disc space. For eachspreading member, one of the distal extension members is longer than theother distal extension member.

According to another aspect, a spreader instrument is provided thatincludes a distal spreader assembly for insertion in the space betweenbony structures and a proximal actuator assembly for actuating thespreader assembly to separate the bony structures. The distal spreaderassembly includes a pair of spreading members each having a pair ofdistal extensions positionable in the spinal disc space. Each spreadingmember includes a stepped region to increase the spacing between thespreading members.

These and other aspects of the invention will be apparent from thefollowing description of the illustrated embodiments.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagrammatic illustration of a spreader instrument.

FIG. 2 is an elevation view of one embodiment of a spreader instrumenthaving spreading members positioned in a space between adjacent bonystructures in an unactuated state.

FIG. 3 is an elevation view of the spreader instrument of FIG. 2 in anactuated state.

FIG. 4 is an elevation view of a portion of the side of the actuatedspreader instrument opposite the side shown in FIG. 3.

FIG. 5 is a plan view looking toward the bottom of the spreaderinstrument of FIG. 2.

FIG. 6 is a perspective view of a distal spreader assembly comprising aportion of the spreading instrument of FIG. 2.

FIG. 7 is another perspective view of the distal spreader assembly ofFIG. 6.

FIG. 8 is a sectional view through the spreading members of the distalspreader assembly of FIG. 6.

FIG. 9 is an elevation view looking at the side of a first spreadingmember of the distal spreader assembly of FIG. 6.

FIG. 10 is an elevation view looking at the contact surface of thespreading member of FIG. 6.

FIG. 11 is an elevation view looking at the side of the second spreadingmember of the distal spreader assembly of FIG. 6.

FIG. 12 is a perspective view of another embodiment of a distal spreaderassembly.

FIG. 13 is another perspective view of the distal spreader assembly ofFIG. 12.

FIG. 14 is a sectional view through the spreading members of the distalspreader assembly of FIG. 12.

FIG. 15 is an elevation view looking at the side of a second spreadingmember of the distal spreader assembly of FIG. 12.

FIG. 16 is an elevation view looking at the contact surface of thespreading member of FIG. 15.

FIG. 17 is an elevation view looking at the side of the first spreadingmember of the distal spreader assembly of FIG. 12.

FIG. 18 is an elevation view of another embodiment spreader instrumentin an unactuated position.

FIG. 19 is an elevation view of the spreader instrument of FIG. 18 in anactuated position.

FIG. 20 is an elevation view of the spreader instrument of FIG. 18 in anactuated position and having an alternate distal end arrangement toprovide greater spreading distance capability.

FIG. 21 is a plan view of the spreader instrument of FIG. 18.

FIG. 22 is a perspective view of one embodiment spreading member useablewith, for example, the spreader instrument of FIG. 18.

FIG. 23 is a bottom plan view of the spreading member of FIG. 22.

FIG. 24 is a top plan view of the spreading member of FIG. 22.

FIG. 25 is a detail view of a portion of the spreading member of FIG.22.

FIG. 26 is a perspective view of another embodiment spreading memberuseable with, for example, the spreader instrument of FIG. 18.

FIG. 27 is a bottom plan view of the spreading member of FIG. 26.

FIG. 28 is a perspective view of a pair of the spreading members ofFIGS. 26 and 27 in an operative orientation relative to one another.

FIG. 29 is an elevation view in partial section of one operativeorientation for a pair of the spreading members shown in FIGS. 22-25.

FIG. 30 is an elevation view of another operative orientation for a pairof the spreading members shown in FIGS. 22-25.

FIG. 31 is a perspective view of the spreading members of FIG. 30positioned in a disc space between adjacent vertebrae of the spinalcolumn.

FIG. 32 is a plan view looking toward the bottom of the upper spreadingmember of FIG. 31 positioned in the disc space.

FIG. 33 is a perspective view showing insertion of a spinal implant intothe disc space between the spreading members of FIG. 31.

FIG. 34 is a perspective view of another embodiment spreading member.

FIG. 35 is a perspective view of another embodiment spreading member.

FIG. 36 is a plan view looking toward the bottom of the spreading memberof FIG. 35.

FIG. 37 is a plan view looking toward the bottom of another embodimentspreading member.

FIG. 38 is a perspective view of another embodiment spreading member.

FIG. 39 is a perspective view of the spreading member of FIG. 38 guidinga cutting instrument.

FIG. 40 is a perspective view of another embodiment spreading member.

FIG. 41 is a perspective view of the spreading member of FIG. 40 lookingin a direction opposite that of FIG. 40.

FIG. 42 is a perspective view of another embodiment spreading member.

FIG. 43 is a bottom plan view of the spreading member of FIG. 42.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiment illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended. Any such alterations and furthermodifications in the illustrated device and any such furtherapplications of the principles of the invention as illustrated thereinare contemplated as would normally occur to one skilled in the art towhich the invention relates.

Referring to FIG. 1, a diagrammatic illustration of one embodiment of aspreader instrument 10 for insertion into the space between adjacentbony structures and for spreading the adjacent bony structures is shown.Spreading instrument 10 includes a proximal actuator assembly 12 and adistal spreader assembly 14. Actuator assembly 12 provides remoteactuation of spreader assembly 14 when spreader assembly 14 ispositioned within the space between adjacent bony structures. Actuatorassembly 12 also releasably maintains spreader assembly 14 in theactuated position. Spreader instrument 10 can be used to access thespace between adjacent bony structures in an open or minimally invasiveprocedure. Additionally, actuator assembly 12 can include an adjustmentmechanism 16 to effect an adjustment of the actuated position ofspreader assembly 14 achieved through actuator assembly 12.

Proximal actuator assembly 12 includes any device or mechanism capableof adjusting the position or orientation of distal spreader assembly 14.Actuator assembly 12 may include linkage systems, wire systems, gearsystems, and flexible adjustment systems, for example. Actuator assembly12 may include linear and/or rotationally moving elements. Actuatorassembly 12 may be rigidly fixed to spreader assembly 14, movably fixedto spreader assembly 14, or a combination of rigid and movable fixation.Suitable examples of actuator assembly 12 components include solid shaftlike elements, bar stock, tubular elements, rod-like elements, linkages,elastically-deformable members, and articulating connectors, forexample. Actuator assembly 12 can be biased by a spring, resilient hingeor other means to a normal position in which spreader assembly 14 isunactuated, actuated, or at some position therebetween.

Adjustment mechanism 16 can position and/or maintain spreader assembly14 in any one of a number of actuated states, and is provided with meansfor securing one or more components of actuator assembly 12 in aparticular position. Such means can include a rod and stop membermovably engageable along the rod, a geared mechanism, a force fit orwedge mechanism, a pivoting locking mechanism, a rotational lockingmechanism, one or more clamping members, an interference fit betweencomponents of actuator assembly 12, and an interference fit between oneor more components connected to and extending between the components ofactuator assembly 12, for example.

Distal spreader assembly 14 can include a pair of spreading membersmovable away from one another by actuator assembly 12 to spread adjacentbony structures. The spreading members can be coupled to actuatorassembly 12 for movement in parallel relation to one another, althoughnon-parallel movement is also contemplated. Distal spreader assembly 14can include a low profile arrangement in the unactuated state forinsertion of the spreading members into a space between the adjacentbony structures. Such low profile arrangement can be provided by nestingthe spreading members, collapsing of the spreading members, overlappingthe spreading members, and/or compressing the spreading members. Thespreading members of spreader assembly 14 can each be configured toconform to the profile of the bony structure of which it contacts. Eachspreading member can include means for engaging the bony structure toresist movement of the spreading members relative to the bony structure.Such engagement means includes pitting, knurling, serrations, teeth,ridges, barbs, spikes, peeks and valleys, grooves, concave curvature,and convex curvature.

One embodiment of a spreader instrument 20 will be described withreference to FIGS. 2-4. This embodiment of spreader instrument 20includes actuator assembly 21, distal spreader assembly 90 and anoptional adjustment mechanism 45. Actuator assembly 21 includes a firsthandle 22 pivotally coupled to a second handle 24 about a fastener 26.Other coupling arrangements are also contemplated, such as an integralhinge or separate hinge mechanism. A first spring member 42 extendsalong first handle 22 and is coupled thereto with pin 42 a. A secondspring member 44 extends along second handle 24 and is coupled theretowith pin 44 a. Spring members 42, 44 are leaf springs that areinterconnected at their distal ends to spring bias handles 22, 24 awayfrom one another to an unactuated position, shown in FIG. 2. Handles 22,24 are moved to an actuated position by moving handles 22, 24 toward oneanother against spring members 42, 44, as shown in FIG. 3.

Adjustment mechanism 45 is provided to adjust and/or secure handles 22,24 and thus spreader assembly 90 in any one of a number of actuatedpositions. Adjustment mechanism 45 includes a connecting member 46pivotally coupled at a distal end 46 b to second pin 44 a. Connectingmember 46 extends through an aperture of a first handle extension 22 bto proximal end 46 a, and pivots as handles 22, 24 move toward or awayfrom one another. An adjustment member 48 located between handleextension 22 b and proximal end 46 a is movable along connecting member46. In the illustrated embodiment, connecting member 46 is threaded andadjustment member 48 is a hand knob threadingly coupled thereto.Proximal end 46 a of connecting member 46 can be non-threaded andenlarged to retain adjustment member 48 on connecting member 46.Adjustment member 48 contacts handle extension 22 b to maintain handles22, 24 and distal spreader assembly 90 in any one of a number ofactuated positions. Adjustment member 48 can be threaded toward proximalend 46 a of connecting member 46 in the direction opposite arrow P. Thisallows handles 22, 24 to move along connecting member 46 and returntoward their unactuated position when released until either adjustmentmember 48 contacts handle extension 22 b or the handles 22, 24 andspreader assembly 90 are completely unactuated. Adjustment member 48 canbe threaded along connecting member 46 in the direction of arrow Ptoward handle extension 22 b to engage or move handles 22, 24 toward oneanother for actuation.

Distal spreader assembly 90 includes a first spreading member 50 and asecond spreading member 70. First spreading member 50 includes aproximal portion 52 attachable to actuator assembly 21. An extensionmember 54 extends distally from proximal portion 52. Second spreadingmember 70 includes a proximal portion 72 attachable to actuator assembly21. An extension member 74 extends distally from proximal portion 72.

As shown in FIG. 4, spreader instrument 20 is rotated 180 degrees aboutlongitudinal axis L. First handle 22 is pivotally coupled at its distalend 22 a to a proximal end 30 a of a first link member 30. Second handle24 is pivotally coupled at its distal end 24 a to a proximal end 28 a ofa second link member 28. First link member 30 extends to a distal end 30b, and second link member 28 extends to a distal end 28 b. Link members28, 30 cross one another to form an X-shape in their actuated state asshown in FIGS. 3 and 4. Link members 28, 30 are pivotally couple to oneanother about central fastener 40 (FIG. 2) of actuator assembly 21. Theoverlapping portions of the crossed link members 28, 30 can be recessedso that the distal and proximal end portions of link members 28, 30extend over one another, as shown with recessed portions 28 c n FIG. 4and recessed portion 30 c in FIG. 3.

Proximal portion 52 of first spreading member 50 includes a proximalslot 56 through which fastener 35 extends. Proximal portion 52 furtherincludes a distal hole 58 through which fastener 39 extends. Fastener 35rotatably and slidably couples proximal portion 52 to actuator assembly21 at the connection between distal end 22 a of first handle 22 andproximal end 30 a of first link member 30. Fastener 39 rotatably couplesproximal portion 52 to distal end 28 b of second link member 28. Secondspreading member 70 includes a proximal portion 72 attachable toactuator assembly 21. Proximal portion 72 includes a proximal slot 76through which fastener 33 extends. Proximal portion 72 further includesa distal hole 78 through which fastener 37 extends. Fastener 33rotatably and slidably couples proximal portion 72 to actuator assembly21 at the connection between distal end 24 a of second handle 24 andproximal end 28 a of second link member 28. Fastener 37 rotatablycouples proximal portion 72 to distal end 30 b of first link member 30.

When actuator assembly 21 is in an unactuated state as shown in FIG. 2,spreading members 50, 70 are positioned adjacent one another. Asactuator assembly 21 is actuated by moving handles 22, 24 toward oneanother, spreading members 50, 70 can move away from and remain parallelduring such movement. The rotatable and slotted engagement of proximalportions 52, 72 via fasteners 35, 33 in slots 56, 76, respectively,allows the relative longitudinal position between actuator assembly 21and spreading members 50, 70 to vary in accordance with the amount ofactuation provided between spreading members 50, 70.

In operation, distal ends 22 a, 24 a of handles 22, 24 move away fromone another by the pivoting of handles 22, 24 about fastener 26. Inaddition, distal ends 28 b, 30 b of link members 28, 30 move away fromone another by the pivoting of link members 28, 30 about fastener 40.This pivoting movement of the components of actuator assembly 21 causesthe length of actuator assembly 21 to reduce along longitudinal axis L.Spreading members 50, 70 rotate about respective ones of the fasteners39, 37, respectively, as distal ends 28 b, 30 b of link members 28, 30are moved away from one another. Fasteners 35, 33 rotate within and movedistally in respective ones of the slots 56, 76 as distal ends 22 a, 24a move away from one another. The movement of fasteners 35, 33 in slots56, 76 accommodates the reduction in length of actuator assembly 21along axis L, while the rotation of fasteners 35, 33 in slots 56, 76allows spreading members 50, 70 to remain parallel to one another asactuator assembly 21 is actuated and unactuated.

As shown in FIG. 5, spreader instrument 20 can be provided with angledoffsets in actuator assembly 21 and spreader assembly 90 to assist inkeeping spreader instrument 20 out of the way of the surgeon. In FIG. 5,handles 22, 24 for a proximal portion 21 a of actuator assembly 21extending along axis A1 and a distal portion 21 b extending along axisA2. Link members 28, 30 also extend along axis A2. Axis A1 forms angleC1 with axis A2. Angle C1 can vary from 180 degrees to 90 degrees orless. It is also contemplated that angle C1 can range from 180 degreesto 135 degrees. One specific embodiment contemplates an angle C1 of 170degrees. Another specific embodiment contemplates an angle C1 of 0degrees

Proximal portions 52, 72 of spreading members 50, 70 of distal spreaderassembly 90 extend along axis B1. Proximal portions 52, 72 are coupledto one side of actuator assembly 21 such that axis B1 is offset from andextends parallel to axis A2. In one embodiment, it is contemplated thatspreader assembly 90 can be coupled to the working side of spreadinginstrument 20 so that actuator assembly 21 is offset laterally fromspreader assembly 90, providing additional space in the surgeon'sapproach to the operative site. Extension members 54, 74 extend along anaxis B2 that forms angle C2 with axis B1. Angle C2 can vary from 180degrees to 90 degrees or less. It is further contemplated that angle C2can vary from 180 degrees to 135 degrees. One specific embodimentcontemplates an angle C2 of 170 degrees. Another specific embodimentcontemplates an angle C2 of 180 degrees.

Referring to FIGS. 6-11, spreading member 50 includes an enlargedopening 56 a about slot 56 so that the head of fastener 35 can berecessed at least partially therein. The shaft of fastener 35 extendsthrough slotted portion 56 b. Similarly, spreading member 70 includesslot 76 with an enlarged opening 76 a about slotted portion 76 b so thatthe head of fastener 33 can be recessed at least partially therein. Hole58 of spreading member 50 includes an enlarged opening 58 a in which thehead of fastener 39 can be recessed, and the shaft of fastener 39extends through hole portion 58 b. Similarly, spreading member 70includes hole 78 with an enlarged opening 78 a about hole portion 78 bso that the head of fastener 37 can be recessed at least partiallytherein.

Spreading member 50 includes a concavely curved end wall 60 extendingfrom proximal portion 52 to extension member 54. Spreading member 70includes a concavely curved end wall 80 extending from proximal portion72 to extension member 74. End walls 60, 80 can abut against the bonystructure adjacent the space in which extension members 54, 74 areinserted to limit the insertion depth of extension members 54, 74 intothe space.

Extension member 54 and extension member 74 each include a configurationthat allows the extensions members 54, 74 to be positioned adjacent oneanother in a low profile arrangement for insertion into the spacebetween the adjacent bony structures. Extension member 54 includes alaterally oriented flange portion 54 a and a vertically oriented webportion 54 b extending along flange portion 54 a. Flange portion 54 aincludes a contact surface 54 c opposite web portion 54 b. Flangeportion 54 a and web portion 54 b define a receptacle 54 d. Extensionmember 74 includes a laterally oriented flange portion 74 a and avertically oriented web portion 74 b extending along flange portion 74a. Flange portion 74 a includes a contact surface 74 c opposite webportion 74 b. Flange portion 74 a and web portion 74 b define areceptacle 74 d. Receptacle 74 d is sized to receive web portion 54 b,and receptacle 54 d is sized to receive web portion 74 b, allowingextension members 54, 74 to be placed in a nested configuration whenspreader instrument 20 is unactuated and spreading members 50, 70 areplaced against or adjacent to one another.

Flange portion 54 a includes a ramped surface 62 opposite contactsurface 54 c that transitions into proximal portion 52, and web portion54 b includes a ramped surface 64 opposite contact surface 54 c thattransitions into proximal portion 52. Similarly, flange portion 74 aincludes a ramped surface 82 opposite contact surface 74 c thattransitions into proximal portion 72, and web portion 74 b includes aramped surface 84 opposite contact surface 74 c that transitions intoproximal portion 72. The ramped transition surfaces facilitate thenesting relationship between extension members 54, 74 when proximalportions 52, 72 are positioned adjacent one another.

In one form, spreading member 50 and spreading member 70 are positionedadjacent one another and in contact with one another along their entirelength in the low profile position. In another form, at least extensionmembers 54, 74 are positioned adjacent to one another and in contactalong their entire length in the low profile orientation. This lowprofile orientation facilitates positioning of spreading members 50, 70as far as possible in the disc space to obtain an even distraction orspreading of the adjacent vertebrae in the distal and proximal regionsof the disc space.

Contact surfaces 54 c, 74 c can have a profile that maximizes thesurface area contact with the adjacent bony structure. For example,contact surface 54 c, 74 c can have a convex profile that matches thegeometry of the portion of the endplates of vertebrae V1 and V2 alongwhich the extension members 54, 74 are positioned, as shown in FIGS. 2and 3. Such matching geometry maintains extension members 54, 74 inposition relative to the vertebral endplate, and also spreads thedistraction or spreading load over a greater area of the bony structure,reducing potential damage to the bony structure that might be caused bydistraction or spreading forces concentrated on portions of the adjacentendplate. The matching geometry also provides a self-centering effect toassist in proper positioning of extension members 54, 74 in the spacerelative to the bony structures.

Contact surfaces 54 c, 74 c can be smooth or have surface features thatengage the bony structure, such as the grooves forming the ridges shownin FIGS. 2-11 that extend transversely to convex curvature of therespective bone contacting surface. Examples of other surface featuresinclude pitting, knurling, serrations, teeth, ridges, barbs, spikes,peeks and valleys, grooves, concave curvature, and convex curvature, forexample.

In one specific embodiment, each extension member 54, 74 can be providedwith a maximum thickness t of 6 millimeters, and receptacles 54 d, 74 deach have a depth of 3 millimeters. Thus, extension members 54, 74 canhave an overall maximum height of 9 millimeters between contact surfaces54 c, 74 c when spreader assembly 90 is in its unactuated position andspreading members 50, 70 are nested relative to one another. Thus, inthe specific illustrated embodiment, the nested relationship provides atleast a 25% reduction in height along the entire length of extensionmembers 54, 74 than would be provided in a non-nested relationship.Extension members 54, 74 can have a width W of 8 millimeters, and webportions 54 b, 74 b occupy half of width W. Extension members 54, 74 canalso be provided with a length D of 40 millimeters, or other length Dsuch that the extension members 54, 74 extend across a substantialportion of a disc space providing even and complete separation of theadjacent vertebrae. It is to be understood that other embodimentscontemplate other maximum heights, widths and lengths for extensionmembers 54, 74.

The moment of inertia and section modulus provided by extension members54, 74 maintains deflection of extension members 54, 74 withinacceptable limits even with long lengths D for extensions members 54,74. Accordingly, extension members 54, 74 can be provided with length Dthat extends substantially across the adjacent vertebral endplate, anduniform distraction or spreading of the vertebrae and force distributionalong the vertebrae can be achieved. The low profile, nestedconfiguration of extension members 54, 74 in the unactuated positionfacilitates insertion into a collapsed or partially collapsed disc spaceor through a small opening to the space between adjacent bonystructures.

Referring now to FIGS. 12-17, another embodiment of a distal spreaderassembly 190 is provided. Spreader assembly 190 can be mounted toactuator assembly 21 such as discussed above with respect to spreaderassembly 90. Spreader assembly 190 includes a first spreading member 150and a second spreading member 170. First spreading member 150 includes aproximal portion 152 attachable to actuator assembly 21. An extensionmember 154 extends distally from proximal portion 152. Second spreadingmember 170 includes a proximal portion 172 attachable to actuatorassembly 21. An extension member 174 extends distally from proximalportion 172.

Proximal portion 152 includes a proximal slot 156 through which fastener35 extends. Proximal portion 152 further includes a distal hole 158through which fastener 39 extends. Fastener 35 rotatably and slidablycouples proximal portion 152 to actuator assembly 21 at the connectionbetween distal end 22 a of first handle 22 and proximal end 30 a offirst link member 30. Fastener 39 rotatably couples proximal portion 152to distal end 28 b of second link member 28. Second spreading member 170includes a proximal portion 172 attachable to actuator assembly 21.Proximal portion 172 includes a proximal slot 176 through which fastener33 extends. Proximal portion 172 further includes a distal hole 178through which fastener 37 extends. Fastener 33 rotatably and slidablycouples proximal portion 172 to actuator assembly 21 at the connectionbetween distal end 24 a of second handle 24 and proximal end 28 a ofsecond link member 28. Fastener 37 rotatably couples proximal portion172 to distal end 30 b of first link member 30.

Spreading member 150 includes an enlarged opening 156 a about slot 156so that the head of fastener 35 can be recessed at least partiallytherein. The shaft of fastener 35 extends through a slotted portion 156b. Similarly, spreading member 170 includes slot 176 including anenlarged opening 176 a about slotted portion 176 b so that the head offastener 33 can be recessed at least partially therein. Hole 158 ofspreading member 150 includes an enlarged opening 158 a in which thehead of fastener 39 can be recessed, and the shaft of fastener 39extends through hole portion 158 b. Similarly, spreading member 170includes an enlarged opening 178 a about hole 178 so that the head offastener 37 can be recessed at least partially therein with the shaftextending through hole portion 178 b.

When actuator assembly 21 is in an unactuated state as shown in FIG. 2,spreading members 150, 170 are positioned adjacent one another. Asactuator assembly 21 is actuated by moving handles 22, 24 toward oneanother, spreading members 150, 170 can move away from and remainparallel during such movement in the manner discussed above with respectto spreader assembly 90, as shown in FIG. 3.

Spreading member 150 includes a concavely curved end wall 160 extendingfrom proximal portion 152 to extension member 154. Spreading member 170includes a concavely curved end wall 180 extending from proximal portion172 to extension member 174. End walls 160, 180 can abut against thebony structure adjacent the space in which extension members 154, 174are inserted to limit the insertion depth of extension members 154, 174into the space.

Extension member 154 and extension member 174 each include aconfiguration that allows the extensions members 154, 174 to bepositioned adjacent one another in a low profile arrangement forinsertion into the space between the adjacent bony structures. Extensionmember 154 includes a lateral flange portion 154 a and a web portion 154b extending along flange portion 154 a. Flange portion 154 a includes acontact surface 154 c opposite web portion 154 b. Flange portion 154 aand web portion 154 b define a receptacle 154 d. Extension member 174includes a flange portion 174 a and a web portion 174 b extending alongflange portion 174 a. Flange portion 174 a includes a contact surface174 c opposite web portion 174 b. Flange portion 174 a and web portion174 b define a receptacle 174 d. Receptacle 174 d is sized to receiveweb portion 154 b, and receptacle 154 d is sized to receive web portion174 b, allowing extension members 154, 174 to be placed in a nestedconfiguration when spreader instrument 20 is unactuated and spreadingmembers 150, 170 are placed against or adjacent to one another. Webportions 154 b, 174 b are provided with a uniform height along therespective flange portion 154 a, 174 a, allowing the height of thenested extension members 154, 174 to be minimized along the entirelength thereof.

Flange portion 154 a includes a ramped surface 162 opposite contactsurface 154 c that transitions into proximal portion 152, and webportion 154 b includes a ramped surface 164 opposite contact surface 154that transitions into proximal portion 152. Flange portion 174 aincludes a ramped surface 182 opposite contact surface 174 c thattransitions into proximal portion 172, and web portion 174 b includes aramped surface 184 opposite contact surface 174 c that transitions intoproximal portion 172. The ramped transition surfaces facilitate thenesting relationship between extension members 154, 174.

Contact surfaces 154 c, 174 c can include a relatively flat profilealong flange portions 154 a, 174 a. In one embodiment, contact surfaces154 c, 174 c includes a number of surface features that include pitsformed by a chemical photo-etching process. The process can produce manyvarious patterns, ranging from a very fine surface roughness to a verycoarse surface roughness. The patterns of etching can be controlled byusing computer-generated negatives of the desired pattern. Bycontrolling the surface area affected by the photo-etching and theetching depth, the strength of the respective extension member 154, 174can be maintained in close proximity to its original, unetched strength.In comparison, an extension member including surface features formed bymechanical cutting or abrasion requires a greater thickness to maintainthe same bending strength after placement of the surface features thandoes an extension member with chemically etched surface features. Thus,the thickness of flange portions 154 a, 174 a can be minimized toprovide a low profile spreader assembly with bone engagement structureson the spreading member for insertion into small spaces between adjacentbony structures.

In one specific embodiment, each extension member 154, 174 can beprovided with a thickness t of 3.5 millimeters, and recesses 154 d, 174d each have a depth of 2 millimeters. Thus, extension members 154, 174can have an overall height of 5 millimeters between contact surfaces 154c, 174 c when spreader assembly 190 is in its unactuated position andspreading members 150, 170 are nested relative to one another. Thus, inthe specific illustrated embodiment, the nested relationship provides atleast a 28% reduction in height than would be provided in a non-nestedrelationship. In the specific embodiment, extension members 154, 174 canhave a width W of 5 millimeters, and web portions 154 d, 174 d occupyhalf of width W. Extension members 154, 174 can also be provided with alength D of 32 millimeters, or other length D such that the extensionmembers 154, 174 extend across a substantial portion of a disc spaceproviding even and uniform separation of the adjacent vertebrae acrossthe disc space. It is to be understood that other embodimentscontemplate other maximum heights, widths and lengths for extensionmembers 154, 174.

The moment of inertia and section modulus provided by extension members154, 174 maintains deflection of extension members 154, 174 withinacceptable limits even with long lengths D. The low profile unactuatedheight of extension members 154, 174 and their parallel relationshipallow extension members to be completely inserted in the space betweenthe adjacent bony structures before distraction or spreading. Thecontrolled deflection of extension members 154, 174 provides uniformspreading or distraction of the vertebrae across the disc space,facilitating endplate and disc space preparation and implant insertion.

Referring back to FIGS. 2-3, techniques employing the spreaderinstrument will be described with reference to spreader instrument 20,it being understood that the techniques described also have applicationwith the other embodiments discussed herein and in surgical proceduresother than spinal surgery. In FIG. 2 spreader instrument 20 has areduced profile configuration for insertion into a collapsed disc spaceD between vertebrae V1 and V2. Actuator assembly 21 is actuated to movespreading members 50, 70 away from one another in parallel relation. Inone embodiment, actuator assembly 21 moves spreading members 50, 70 awayfrom one another in parallel relation while actuator assembly 21simultaneously moves longitudinally relative to the spreading members50, 70. It should be understood, however, that aspects of the inventioncontemplate that the spreading members are not moved parallel to oneanother and/or are not parallel to one another.

The spreading members 50, 70 contact an endplate of a respective one ofthe vertebrae V1 and V2. Spreading members 50, 70 are moved further awayfrom one another with actuator assembly 21 to restore collapsed discspace D from its collapsed height H1 to a restored height H2. Thereafterthe surgeon can insert instruments and the like into disc space D toremove bone material, disc material and the like to prepare the discspace for subsequent procedures, such as the insertion of an interbodydevice, fusion device, graft material, or artificial disc, for example.Spreader instrument 20 can maintain disc space distraction during suchprocedures. Since, contact surfaces 54 c, 74 c occupy relatively smallareas of the vertebral endplates, it is contemplated that the entireprocedure can be conducted with spreader instrument 20 in the discspace. It is further contemplated that spreader instrument 20 can beeasily and quickly repositioned in the disc space for completion ofprocedures in the areas previously occupied by the spreader instrument.

One specific application contemplates distracting or spreading adjacentvertebrae of the spine. Any number of approaches to the spine arecontemplated, including anterior, posterior, lateral, postero-lateral,antero-lateral approaches, for example, and also in minimally invasiveand open surgical procedures. Aspects of the spreader instrumentembodiments discussed can be employed in spreader instruments adaptedfor endoscopic, laparoscopic, and/or thorascopic procedures. Thespreader instrument can also be employed to spread adjacent bonystructures in locations other than the spine.

In one embodiment, the spreading members are provided with a ceramiccoating. A ceramic coating can provide a low friction surface treatmentthat reduces or eliminates glare from the distal spreader assembly,enhancing surgeon viewing of the operative site. It is furthercontemplated that the spreading instruments can be made from anymaterial acceptable for fabrication of surgical instruments.

Another embodiment of a spreader instrument 220 will be described withreference to FIGS. 17-20. This embodiment of spreader instrument 220includes an actuator assembly 221, a distal spreader assembly 290 and anoptional adjustment mechanism 245. Actuator assembly 221 includes afirst handle 222 pivotally coupled to a second handle 224 about afastener 226. A first spring member 242 extends between first handle 222and second handle 224 along and about a pin 244. Spring member 242 is acoil spring that biases handles 222, 224 away from one another so thatspreader assembly 290 of spreader instrument 220 is biased to a normallyclosed position, as shown in FIG. 18. Handles 222, 224 are moved to anactuated position by moving handles 222, 224 toward one another againstspring member 242, compressing spring member 242 along pin 244 as shownin FIG. 19.

Adjustment mechanism 245 is provided to adjust and/or secure handles222, 224 and thus spreader assembly 290 in any one of a number ofactuated positions. Adjustment mechanism 245 includes pin 244 pivotallyconnected to handle 222 and extending through handle 224. Spring member242 extends about the portion of pin 244 between handles 222, 224. Anadjustment member 248 located on the end of pin 244 extending throughhandle 224 is movable along pin 244 to adjust and/or maintain therelative positioning between handles 222, 224. In the illustratedembodiment, pin 244 can be threaded and adjustment member 248 can be ahand knob threadingly coupled thereto. The outer end of pin 244 can benon-threaded and enlarged to retain adjustment member 248 on pin 244.

Adjustment member 248 can contact second handle 224 to maintain handles222, 224 and distal spreader assembly 290 in any one of a number ofactuated positions. Adjustment member 248 can be threaded toward thedirection opposite arrow P to allow handles 222, 224 to return towardtheir unactuated position until either adjustment member 248 contactshandle 224 or the handles 222, 224 and spreader assembly 290 arecompletely unactuated. Adjustment member 248 can be threaded along pin244 in the direction of arrow P toward handle 224 to maintain anactuated position or move handles 222, 224 toward one another foractuation.

First handle 222 is pivotally coupled at its distal end 222 a to aproximal end of a first link member 230. Second handle 224 is pivotallycoupled at its distal end 224 a to a proximal end of a second linkmember 228. Link members 228, 230 cross one another to form an X-shapein their actuated state as shown in FIGS. 19 and 20. Link members 228,230 are pivotally coupled to one another about central fastener 240 ofactuator assembly 221. The overlapping portions of the crossed linkmembers 228, 230 can be recessed so that the distal and proximal endportions of link members 228, 230 can extend over and be aligned withone another, as shown in FIG. 21.

Distal spreader assembly 290 includes a first spreading member 250 and asecond spreading member 270. First spreading member 250 is attachable toa first coupling member 252 of actuator assembly 221. Second spreadingmember 270 is attachable to a second coupling member 272 of actuatorassembly 221. Coupling member 252 includes a distal slot 256 throughwhich fastener 235 extends. Coupling member 252 further includes aproximal hole through which fastener 239 extends. Fastener 235 rotatablyand slidably couples coupling member 252 to a distal end of second linkmember 228 of actuator assembly 221. Fastener 239 rotatably couplescoupling member 252 to a proximal end of first link member 230. Secondcoupling member 272 includes a distal slot 276 through which fastener233 extends. Coupling member 272 further includes a proximal holethrough which fastener 237 extends. Fastener 233 rotatably and slidablycouples coupling member 272 to a distal end of first link member 230.Fastener 237 rotatably couples coupling member 272 to a proximal end ofsecond link member 228.

When actuator assembly 221 is in an unactuated state as shown in FIG.18, spreading members 250, 270 are positioned adjacent one another. Asactuator assembly 221 is actuated by moving handles 222, 224 toward oneanother, spreading members 250, 270 can move away from one another andremain parallel during such movement. The rotatable and slottedengagement of coupling members 252, 272 via fasteners 235, 233 in slots256, 276, respectively, allows the relative longitudinal positionbetween actuator assembly 221 and spreading members 250, 270 to vary inaccordance with the amount of actuation provided, and for spreadingmembers 250, 270 to remain parallel to one another during such movement.It should be understood, however, that other actuator assemblies 221 arecontemplated, including those that provide non-parallel movement ofspreading members 250, 270. Actuator assembly 221 could also beconfigured to move spreading members 250, 270 through, for example, ascissors coupling arrangement between handles 222, 224, a gear rackmechanism, or other actuator assembly arrangement discussed herein.

In operation, the distal ends 222 a, 224 a of handles 222, 224 move awayfrom one another by the pivoting of handles 222, 224 about fastener 226.In addition, the distal ends of link members 228, 230 move away from oneanother by the pivoting of link member 228, 230 about fastener 240. Thispivoting movement of the components of actuator assembly 221 causes thelength of spreader instrument 220 to reduce along longitudinal axis L.Coupling members 252, 272 rotate about respective ones of the fasteners239, 237, respectively, as spreading members 250, 270 are moved awayfrom one another. Fasteners 235, 233 rotate within and move proximallyin respective ones of the slots 256, 276 as spreading members 250, 270move away from one another. The movement of fasteners 235, 233 in slots256, 276 accommodates the reduction in length of actuator assembly 221along axis L, while the rotation of fasteners 235, 233 in slots 256, 276and the rotation of fasteners 239, 237 allows spreading members 250, 270to remain parallel to one another as actuator assembly 221 is actuatedand unactuated.

In the unactuated position of FIG. 18, spreading members 250, 270 arepositioned adjacent one another, and have an overall height H3 thatallows insertion of distal extension members 262, 282 of spreadingmembers 250, 270, respectively, into a spinal disc space or corpectomyspace between adjacent vertebrae. In an actuated state, spreadingmembers 250, 270 can be separated so that a height H4 is providedbetween distal extension members 258, 278. Height H4 can correspond to adesired disc space height prior to disc space preparation, vertebralbody preparation, and/or implant insertion. The configuration ofactuator assembly 221 contemplates that handles 222, 224 are movedtoward one another to move spreading members 250, 270 away from oneanother, which can limit the maximum distraction or separation height H4when the handles contact or are adjacent one another.

Spreading members 250, 270 can be removably coupled to coupling members252, 272, respectively so that spreading members 250, 270 can be readilyinterchanged with, for example, spreading members having different sizesand/or configurations. For example, as shown in FIG. 20, spreadingmembers 350, 370 are attached to actuator assembly 221 and provide amaximum distraction height H5 between distal extension members 362, 382.Height H5 is greater than height H4 since each spreading member 350, 370is provided with a stepped region 354, 384, each of which includes aheight H6. Thus, the amount of distraction available with spreadingmembers 350, 370 is greater than that provided with spreading members250, 270 by two times height H6. Spreading members with a stepped regioncan be employed in, for example, corpectomy procedures where thespreading distance needed between the spreading members is greater thanthat required in disc space procedures.

In one specific example, selecting one spreading member with a steppedregion including a height H6 provides a 15 millimeter spacing betweenthe spreading members when the other spreading member includes nostepped region. If desired, the other spreading member can be replacedwith a second spreading member including a stepped region including aheight H6 that provides an additional 15 millimeter spacing between thespreading members. Thus, an overall spacing of 30 millimeters isprovided between the spreading members. The ability to select and employspreading members with stepped regions of various heights, or with nostepped region, facilitates use of the spreading instrument incorpectomy procedures and other procedures requiring additional space orseparation between the adjacent bony structures may be required.

As shown in FIG. 21, actuator assembly 221 can be provided with a linearconfiguration along its length. Spreading members 250, 270 can beprovided in a generally U-shaped configuration. For example, spreadingmember 270 includes a pair of distal extension members 282, 284extending from a body portion 271. Spreading member 250 can be similarlyprovided with a first distal extension member (not shown) below andaligned with distal extension member 284, and a second distal extensionmember 262 below and aligned with distal extension member 282. Each ofthe spreading members 250, 270 of distal spreader assembly 290 can beoffset to one side of actuator assembly 221 with, for example, an offsetportion 274 extending between body portion 271 and a coupling portion284 engaged with coupling member 272. Similarly, spreading member 250can include an offset portion extending between a body portion and acoupling portion 264 engaged with coupling member 252. The offset ofactuator assembly 221 relative to the spreading members of spreaderassembly 290 facilitates access for disc space preparation, vertebralbody preparation and implant insertion between the spreading members250, 270 while spreading members 250, 270 are positioned in the spacebetween vertebrae.

It is further contemplated that each of the handless 222, 224 can beprovided with a distal portion 222 c, 224 c and a proximal portion 222b, 224 b, respectively. Proximal portions 222 b, 224 b can be pivotallycoupled to respective ones of the distal portions 222 c, 224 c aboutpins 230, 231, respectively. Pins 230, 231 can be configured to lockproximal portions 222 b, 224 b in the position shown in FIG. 20. Whenpins 230, 231 are pressed, proximal portions 222 b, 224 b can be pivotedabout their connection with distal portions 222 c, 224 c in thedirection of arrow 229 and away from spreader assembly 290 to furtherfacilitate access to the operative site.

In FIGS. 22-41 various embodiment spreading members are provided. Thesespreading member embodiments and the spreading member embodimentsdiscussed above can be employed with any of the actuator assemblyembodiments or configurations discussed herein. It is furthercontemplated that spreading member embodiments could be removablyattached to an actuator assembly so that spreading members havingvarious configurations and/or distraction characteristics can be readilyemployed by the surgeon during the surgical procedure or for differentsurgical procedures with the same instrument set or actuator assembly.It is further contemplated that the spreading member embodiments couldbe a permanent and/or integral portion of the spreading instrument.

Referring now to FIGS. 22-25, another embodiment spreading member 400 isprovided that is attachable to, for example, actuator assembly 221.Spreading member 400 includes a body portion 402 and a proximal couplingportion 404 offset from body portion 402 by offset portion 424. A firstextension member 406 and a second extension member 408 extend distallyfrom body portion 402. Body portion 402 further includes a proximal endwall 421 and an opposite distal end wall 422 having a concave surfaceprofile configured to reside against or along the convex curvature of anadjacent vertebral body. Body portion 402 includes an outer surface 403and an opposite inner surface 405 oriented toward the other spreadingmember when assembled with the actuator assembly.

Outer surface 403 and inner surface 405 are spaced from one another toprovide a thickness or depth to body portion 402 that limits deflectionupon application of a spreading load to the adjacent bony structure. Forexample, extension member 406 is spaced laterally from the connection ofspreading member 400 with the actuator assembly 221. Thus, extensionmember 406 is cantilevered laterally relative to extension member 408 bybody portion 402. Loads applied by extension member 406 will tend tobend or deflect body portion 402 such that extension members 406, 408 donot remain aligned with one another. Body portion 402 is provided with athickness between outer surface 403 and inner surface 405 that limitsthe deflection of extension member 406 under the spreading loads to beencountered so that extension members 406, 408 remain aligned with oneanother to facilitate precise endplate preparation and implantinsertion.

A guide member 410 extends along and forms an extension of the innersurface 405 of body portion 402 between a leading end 411 and a trailingend 412. Leading end 411 is positioned distally of body portion 402 andextends between extensions 406, 408. Trailing end 412 is positionedproximally of body portion 402. In the illustrated embodiment, guidemember 410 has a flat, plate-like surface profile opposite body portion402. As discussed further below, guide member 410 facilitates placementof disc space preparation instruments and implants between adjacentspreading members employing guide members 410.

First extension member 406 and second extension member 408 are spaced bya distance W1, and each extension member 406, 408 can be provided with awidth W3. In one embodiment, spreading member 400 is adapted for ananterior approach to the lumbar spine, and width W1 can be about 27millimeters and width W3 can be about 3.5 millimeters. Other widths W1and W3 are contemplated for anterior approaches to the lumbar spine, andfor other approaches to the spine, and for approaches to otheranatomical structures. Extension members 406, 408 can be provided with atapered leading end to facilitate insertion into the spinal disc space,and a height that tapers from body portion 402 to the leading endthereof. Extension members 406, 408 extend along and below inner surface405 of body portion 402 as shown in FIGS. 22-23, and define a spacetherebetween that can receive instruments and/or implants.

Each of the extension members 406, 408 can be provided with boneengaging features, such as teeth 414 shown in FIG. 25. In theillustrated embodiment, three teeth 414 are provided on each extensionmember 406, 408. Teeth 414 are located so that when extension members406, 408 are positioned in a spinal disc space and leading end wall 422of body portion 402 is adjacent to or in contact with the vertebralbody, teeth 414 can bite into or engage the cortical rim of the adjacentvertebral endplate as spreader instrument 220 is actuated to spread theadjacent vertebrae. Teeth 414 can anchor the spreader instrument to thevertebrae and resist movement of the spreader instrument relative to thevertebrae during the surgical procedure. In the illustrated embodiment,teeth 414 are V-shaped with a sharp outer end to penetrate into theadjacent bony structure.

Coupling portion 404 includes proximally opening channel having an entryportion 416 and a locking member receiving portion 418. A lockingmember, such as locking members 253, 273 shown in FIGS. 18-21, include afirst portion positionable through entry portion 416 and a larger,second portion positionable in receiving portion 418. The larger portionis too large to pass through entry portion 416. When it is desired toengage spreading member 400 to an actuator assembly, locking member 253,for example, can be pressed downwardly so that its larger first portionis located out of the insertion path of coupling portion 404 intocoupling member 252. The smaller portion of locking member 253 islocated in the insertion path, and entry portion 416 can slide over thesmaller portion until the smaller portion of locking member 253 ispositioned in receiving portion 418 and the larger portion is alignedwith receiving portion 418. Locking member 253 is then released andspring-biased to return the larger portion into receiving portion 418,providing an interference fit therewith and locking spreading member 400to actuator assembly 221.

In FIGS. 26 and 27 there is shown another embodiment spreading member450 attachable to a spreader instrument, such as, for example, spreaderinstrument 220. Spreading member 450 can be similar to spreading member400 discussed above, and includes a body portion 452 having extensionmembers 456, 458 extending from distal end wall 472 adjacent innersurface 455 of body portion 452. An offset portion 474 extends betweenbody portion 452 and a coupling portion 454. Extension members 456, 458can be provided with bone engaging features 464.

A guide member 460 extends between a leading end 461 located distally ofdistal end wall 472 and an opposite trailing end 462 located proximallyof proximal wall 471. When compared to guide member 410 above, guidemember 460 extends proximally a greater distance to provide a greatersurface area along which to guide disc space preparation instrumentsand/or implant insertion instruments. In each embodiment, leading ends411, 461 of guide members 410, 460 can extend into the disc space atleast along the cortical rim of the adjacent vertebra. For spreadingmember 400, trailing end 412 can be spaced about 42.5 millimeters fromleading end 411. For spreading member 450, trailing end 462 can bespaced about 60 millimeters from leading end 461. Other lengths betweenthe leading ends and trailing ends of guide members 410, 460 are alsocontemplated, ranging from 7 millimeters to 80 millimeters or more, forexample.

In FIG. 28 a pair of spreading members 450, 480 are shown separated fromone another in an actuated position without an actuator assembly.Spreading member 480 is a mirror image of spreading member 450, andincludes a body portion 482 having a distal end wall 499 and a pair ofextension members 486, 488 extending distally from distal end wall 499.A coupling portion 484 extends proximally from body portion 452.Implants and implant insertion instruments can be guided into the discspace between spreading members 450, 480 along the flat surfaces ofguide members 460, 490 adjacent the inner surfaces 455, 485.

In FIG. 29 a pair of spreading members 400, 430 are shown in partialsection through guide members 410, 440. Spreading members 400, 430 areseparated from one another in an actuated positioned without an actuatorassembly. Spreading member 430 is a mirror image of spreading member400, and includes a body portion 432 having a distal end wall 449 and apair of extension members (only extension member 438 shown) extendingdistally from distal end wall 449. A coupling portion 434 extendsproximally from body portion 432. Implants and implant insertioninstruments can be guided into the disc space along the flat surfaces ofguide members 410, 440, which form angle A3 therebetween. In theillustrated embodiment, angle A3 is 0 degrees for parallel endplatepreparation and implant insertion. In FIG. 30, angle A4 is formedbetween guide members so that the spacing between guide members 410, 440tapers distally for lordotic endplate preparation, implant insertion andrestoration. In one embodiment, angle A4 can be 8 degrees. Other anglesare also contemplated based on the desired angle between the adjacentvertebral endplates.

When positioned adjacent the spinal column, as shown in FIGS. 31 and 32,distal end walls 422, 449 of spreading members 400, 430 can abut theadjacent vertebral body 500, 502, respectively, with the extensionmembers 406, 408 of spreading member 400 and the corresponding extensionmembers of spreading member 430 in the spinal disc space 504. Guidemembers 410, 440 have their leading ends, such as leading end 411 shownin FIG. 32, extending into the disc space 504 while trailing end 412 ispositioned proximally of the vertebral bodies 500, 502. The portion ofthe guide member extending into the disc space can protect the implantand/or the outer cortical bone from damage during insertion of theimplant. Extension members 406, 408 can be centered about the sagittalplane 520, or can be offset for an oblique approach or multipleapproaches to the disc space.

As shown in FIG. 33, an implant 506 can be attached to a distal end 508of an insertion instrument 510. Spreading members 400, 430 are spreadapart by an actuator assembly (not shown) to provide a desired spacingbetween vertebrae 500, 502. Implant 506 is positioned between guidemembers 410, 440 and guided into disc space 504 therebetween asinsertion instrument 510 is impacted or pushed forward to the desiredlocation in disc space 504 between vertebrae 500, 502. Implant 506 canfurther be guided laterally between extension members 406, 408 and alsothe extension members of spreading member 430 to maintain the insertionpath into the disc space until the implant is fully seated.

The guide members of spreading members 400, 430, 450, 480 act as a rampto facilitate distraction of the adjacent vertebrae with insertion ofthe implant. The implant enters the space between the guide members attheir trailing ends, and is impacted or pushed toward the distal ends todistract the vertebrae. The guide members protect the cortical bonealong which the guide member extends from damage during implantinsertion, and can prevent the distal extension members from subsidinginto the vertebral endplates by providing a greater load bearing areaduring distraction. The guide members can also reduce friction duringimplant insertion to facilitate implant placement. It is furthercontemplated that the guide members can be formed with or engaged withthe distal extension members and the body portion of the adjacentspreading member to provide rigidity and strength to the guide member.The low profile of the guide members and separation between the distalextension members facilitates viewing of the operative space between thespreading members.

In FIG. 34 there is shown another embodiment spreading member 550useable with a spreader instrument, such as spreader instrument 220.Spreading member 550 can be similar to spreading member 450 discussedabove, and includes a body portion 552 having distal extension members556, 558 extending from distal end wall 572. An offset portion 574extends between coupling portion 554 and body portion 552. Extensionmembers 556, 558 can be provided with bone engaging features 564.

Coupling portion 554 can be provided with a tapered insertion portion566 and a laterally extending locking member receiving portion 568.Receiving portion 568 can receive a locking member to releasably engagespreading member 550 to a spreading instrument with a locking member,such as locking members 253, 273 discussed above. The tapered insertionportion 566 moves the locking member out of alignment with the passageinto which coupling portion 554 is positioned. The locking member can bespring-biased to releasably engage coupling portion 554 in receivingportion 568.

Spreading member 550 further includes a stepped region 560 that extendsvertically between coupling portion 554 and body portion 552. Steppedregion 560 can be provided with a height H6 between coupling portion 554and extensions 556, 558. Stepped region 560 provides greater separationbetween the distal extensions members of adjacent spreading members,thus allowing greater distraction distances between vertebrae to beobtained, as may be desirable in corpectomy procedures.

In FIGS. 35 and 36 a spreading member 600 is provided that is adaptedfor an anterior-oblique approach to the spinal disc space. Spreadingmember 600 includes a body portion 602 and a pair of extension members606, 608 extending distally from body portion 602. An offset portion 624extends to coupling portion 604. Coupling portion 604 includes a detent605 for receiving a spring-loaded ball to couple spreading member 600 toan actuator assembly. Other coupling arrangements discussed herein arealso contemplated.

Spreading member 600 has a central axis 610 between and extendingparallel to extension members 606, 608. Offset portion 624 extends alongan axis 612 oriented at angle A5 to axis 610. One embodimentcontemplates that angle A5 can be in the range from 0 degrees to 90degrees. Another embodiment contemplates that angle A5 can be in therange from 15 degrees to 60 degrees. In one specific embodiment, it iscontemplated that angle A5 can be about 30 degrees.

To accommodate an anterior oblique approach, extension member 606 can belonger than extension member 608 since extension member 606 ispositioned anteriorly of extension member 608 in the disc space. Oneembodiment contemplates that extension member 606 is about 7 millimeterslonger than extension member 608. Another embodiment shown in FIG. 37contemplates a spreading member 650 having a configuration suited for anoblique approach in which extension members 656, 658 have the samelength extending from body portion 652. Spreading member 650 similarlyincludes a central axis 660 and an offset axis 662 extending alongcoupling portion 654 forming angle A5 with central axis 660. Spreadingmember 650 can also be inserted in an anterior-posterior orientationwith at least a portion of the actuator assembly angled relative to axis660.

In FIG. 38 there is shown another spreading member embodiment designatedat 700. Spreading member 700 includes a body portion 702 having a distalend wall 722. First extension member 706 and second extension member 708extend distally from and below end wall 722. Extension members 706, 708include bone engaging features 714. An offset portion 724 extendsbetween a coupling portion 704 and body portion 702. A support surface710 extends along extension member 708, through body portion 702, andalong offset portion 724. An opposite support surface 711 extends alongextension member 706 and through body portion 702. Support surfaces areopen toward the upper sides of extension members 706, 708.

As shown in FIG. 39, support surfaces 710, 711 are adapted to support atleast a blade portion 734 of a cutting instrument 730, such as a chisel.Blade portion 734 extends distally from a shaft portion 732. Bladeportion 734 is movable along support surfaces 710, 711 to remove, forexample, bony material and/or other tissue material located betweenextensions 706, 708 and below support surfaces 710, 711. Extensionmembers 706, 708 remain in contact with and support the adjacentvertebrae as cutting instrument 300 is manipulated to remove bonymaterial between extension members 706, 708.

In FIGS. 40 and 41 there is shown another spreading member embodimentdesignated at 750. Spreading member 750 includes a body portion 752having a distal end wall 772. First extension member 756 and secondextension member 758 extend distally from and are offset below end wall772. Extension members 756, 758 include bone engaging features 764 alonga bone contacting surface thereof. An offset portion 774 extends betweena coupling portion 754 and body portion 752. A support surface 763 isdefined by a receiving slot 760 extending through body portion 752 andabove extension members 756, 758. Receiving slot 760 is adapted toreceive at least a blade portion of a cutting instrument, such ascutting instrument 730 discussed above. The lateral edges of receivingslot 760 are positioned between extensions members 756, 758 so that thebone material supported by extension members 756, 758 remains intact asthe blade portion is moved within slot 760 to remove, for example, bonymaterial and/or other tissue material located between extension members756, 758 and below slot 760. The implant can then be positioned in theprepared disc space in contact with the portions of the vertebral bodiesremoved with the cutting instrument.

It is further contemplated that slot 760 can be provided with a groove761 therealong. Groove 761 can receive a guide member (not shown) on thecutting instrument to maintain movement of the cutting blade within slot760 parallel to extension members 756, 758. Groove 761 is formed insupport surface 763, although other locations about slot 760 are alsocontemplated.

Referring now to FIGS. 42-43, another embodiment spreading member 800 isprovided that is attachable to, for example, actuator assembly 221.Spreading member 800 includes a body portion 802 and a proximal couplingportion 804 offset from body portion 802 by offset portion 824. Anextension member 808 extends distally from body portion 802 adjacent afirst side thereof. Body portion 802 further includes a proximal endwall 826 and an opposite distal end wall 822 having a concave surfaceprofile configured to reside against or along the convex curvature of anadjacent vertebral body. Body portion 802 includes an outer surface 803and an opposite inner surface 805 oriented toward a second spreadingmember when assembled with the actuator assembly, it being understoodthat the second spreading member provides a mirror image of spreadingmember 800 when assembled with the actuator assembly.

Outer surface 803 and inner surface 805 are spaced from one another toprovide a thickness or depth to body portion 802 that limits deflectionthereof upon application of a spreading load to the adjacent bonystructure. A guide member 810 extends along and forms an extension ofthe inner surface 805 of body portion 802 between a leading end 814 anda trailing end 816. Leading end 814 is positioned distally of bodyportion 802 and extends along distal end wall 822 between extensionmember 808 and a guide member extension 812. Guide member extension 812is positioned adjacent a second side of body 802 opposite the first sidefrom which extension member 808 extends. Guide member extension 812extends distally to mimic the shape and length of extension member 808.Trailing end 816 is positioned proximally of body portion 802. In theillustrated embodiment, guide member 810 has a flat, plate-like surfaceprofile opposite body portion 802. As discussed above, guide member 810facilitates placement of disc space preparation instruments and implantsbetween adjacent spreading members employing guide members 810.

Extension member 808 extends from inner surface 805 and includes athickness between an outer surface 830 and an inner surface 832 thatlimits or prevents bending of extension member 808 as it applies aspreading force to the adjacent vertebra. Extension member 808 furtherincludes a length extending from distal end wall 822 that allows outersurface 830 to contact the cortical rim of the adjacent vertebralendplate to apply a spreading force thereto. However, the length isminimized to facilitate implant insertion and/or instrument manipulationlaterally of extension member 808 in the direction opposite guide memberextension 812. Guide member 810 also extends distally for distal endwall 822 along the cortical rim of the adjacent vertebral endplate tofacilitate passage of instruments and/or implants along the cortical riminto the disc space without engaging or catching and damaging the bonymaterial at the cortical rim. In one specific embodiment, extensionmember 808 and guide member 810 extend distally about 4 millimeters fromdistal end wall 822. Other embodiments contemplate other lengths greaterthan about 2 millimeters.

Guide member extension 812 includes an inner surface that lies in thesame plane as inner surface 805. This allows implants and/or instrumentsto be guided into the disc space between spreading members and alongmedial surface 809 of extension 808. The implants and/or instruments canbe provided with a width extending from medial surface 809 that isgreater than the width of spreading member 800 between extension member808 and guide member extension 812. Accordingly, the implant and/orinstruments are not constrained between distal extension members ofspreading member 800. It is further contemplated that extension member808 can be provided with bone engaging features, such as teeth, surfaceroughenings or other surface features as discussed herein to resistmovement of extension member 808 relative to the vertebral endplate.

Other forms for spreading member 800 contemplate a second extensionmember extending distally from body 802 along guide member extension812. The second extension member can be provided with a relatively shortlength to allow instruments and implants to be positioned distallythereof when the second extension member is in the disc space.

The instruments discussed herein can be provided as a kit including anactuator assembly and various pairs of spreading members removablyattachable to the actuator assembly and from which the surgeon canselect depending on the procedure. For example, the kit can include anactuator assembly and any one or combination of a set of singleextension spreading members such as shown in FIG. 6; one or more sets ofdouble extension spreading members forming various angles between guidemembers such as shown in FIGS. 29 and 30; one or more sets of spreadingmembers without guide members and/or for various approaches to the discspace such as shown in FIGS. 34-37; one or more sets of spreadingmembers with an offset region such as shown in FIG. 34; one or more setsof spreading members adapted to guide a cutting instrument, such asshown in FIGS. 39 and 40; and one or more sets of spreading members witha single extension and guide member, such as shown in FIGS. 42-43.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, and that all changes andmodifications that come within the spirit of the invention are desiredto be protected.

What is claimed is:
 1. An instrument for separating bony structures,comprising: an actuator assembly comprising a first handle and a secondhandle; a spreader assembly at a distal end of said actuator assembly,wherein said spreader assembly includes first and second spreadingmembers positionable between the bony structures and movable away fromand toward one another with said actuator assembly, wherein said firstand second spreading members each include: a coupling portion extendingfrom and removably engaged to said actuator assembly; a body portionextending from said coupling portion; a first extension member extendingdistally from a first side of said body portion, said first extensionmember including a bone contacting surface therealong for engaging thebony structure positioned thereagainst; and a second extension memberspaced from said first extension member and extending distally from asecond side of said body portion, said second extension member includinga bone contacting surface therealong for engaging the bony structurepositioned thereagainst; and a linkage assembly comprising a first linkmember pivotally coupled to the first and second handles and a secondlink member pivotally coupled to the first and second handles, the firstand second link members being pivotally coupled to one another, whereinat least one of said first and second spreading members includes astepped region extending vertically from said coupling portion to saidbody portion, said stepped region vertically spacing said body portionand said first and second extension members of said at least one of saidfirst and second spreading members from said body portion and said firstand second extension members of the other of said first and secondspreading members when said actuator assembly is in an unactuatedposition to place said spreading members at a minimum height relative toone another.
 2. The instrument of claim 1, wherein said bone contactingsurfaces each include a convex curvature therealong and a number ofgrooves in said convexly curved portion forming said bone engagementfeatures.
 3. The instrument of claim 1, wherein said body portion ofeach of said first and second spreading members includes an outersurface, an inner surface oriented opposite said bone contactingsurfaces of said first and second extension members, and a distal endwall concavely curved between said first and second extension members.4. The instrument of claim 3, wherein said first and second extensionmembers of each of said first and second spreading members extend fromsaid distal end wall adjacent said inner surface.
 5. The instrument ofclaim 1, wherein for each of said first and second spreading memberssaid first extension member extends distally further than said secondextension member.
 6. The instrument of claim 1, wherein said bodyportion of each of said first and second spreading members includes anouter surface, an inner surface oriented opposite said bone contactingsurfaces of said extension members, a distal end wall, and a proximalend wall, said body portion further comprising a slot extending betweensaid proximal and distal end walls sized to receive a cutting instrumenttherethrough.
 7. The instrument of claim 6, wherein said slot is sizedto guide the cutting instrument between said bone contacting surfaces ofsaid first and second extension members.
 8. The instrument of claim 7,wherein said body portion includes a groove in communication with saidslot to maintain alignment of the cutting instrument.
 9. The instrumentof claim 1, wherein said body portion of each of said first and secondspreading members includes an outer surface, an inner surface orientedopposite said bone contacting surfaces of said first and secondextension members, a distal end wall, and a proximal end wall, said bodyportion further comprising a support surface extending along said innersurface and each of said first and second extension members to support acutting instrument therealong.
 10. An instrument for separating bonystructures, comprising: an actuator assembly comprising a first handleand a second handle; a spreader assembly at a distal end of saidactuator assembly, wherein said spreader assembly includes first andsecond spreading members movable away from and toward one another withsaid actuator assembly, said spreading members each including a bodyportion and a pair of extension members extending distally from saidbody portion, said spreading members further each including a supportsurface extending from a proximal end of said body portion through adistal end of said body portion and on each of said pair of extensionsfor guiding a cutting instrument between said pair of extension members,wherein said support surfaces of said first and second spreading membersface away from one another in opposite directions; and a linkageassembly comprising a first link member coupled to the first and secondhandles and a second link member coupled to the first and secondhandles, the first and second link members being pivotally coupled toone another.
 11. The instrument of claim 10, wherein said body portionof each of said first and second spreading members includes an outersurface, an inner surface oriented toward the inner surface of the otherbody portion, a distal end wall, and a proximal end wall, said bodyportion further comprising a slot defining a portion of said supportsurface, said slot extending between and opening at said proximal anddistal end walls.
 12. The instrument of claim 10, wherein said bodyportion of each of said first and second spreading members includes anouter surface, an inner surface oriented toward the inner surface of theother body portion, a distal end wall, and a proximal end wall, saidsupport surface extending along said inner surface of said body portionand along each of said first and second extension members.
 13. Theinstrument of claim 10, wherein said body portion of at least one ofsaid first and second spreading members includes a stepped regionextending from said actuator assembly, said stepped region spacing saidfirst and second extension members of said at least one of said firstand second spreading members from said first and second extensionmembers of the other of said first and second spreading members withsaid actuator assembly in an unactuated position.
 14. The instrument ofclaim 10, wherein each one of said pair of extension members of each ofsaid spreading members includes a number of teeth extending from a bonecontacting surface thereof.
 15. The instrument of claim 10, furthercomprising an adjustment mechanism coupled to said actuator assembly.16. An instrument for separating adjacent vertebrae, comprising: anactuator assembly comprising a first handle and a second handle; aspreader assembly at a distal end of said actuator assembly, whereinsaid spreader assembly includes first and second spreading memberspositionable between the adjacent vertebrae and movable away from andtoward one another with said actuator assembly, said spreading memberseach including a body portion and first and second extension membersspaced from one another and extending distally from said body portion,said first extension member including a length that is greater than alength of said second extension member; and a linkage assemblycomprising a first link member coupled to the first and second handlesand a second link member coupled to the first and second handles, thefirst and second link members being pivotally coupled to one another.17. The instrument of claim 16, wherein said first and second extensionmembers are adapted for each of said body portions to be positionedalong an anterior-oblique aspect of the adjacent vertebrae.
 18. Theinstrument of claim 16, wherein said first and second extension membersof each of said spreading members each include a number of teethextending from a bone contacting surface thereof.
 19. The instrument ofclaim 16, wherein said body portion of each of said first and secondspreading members includes an outer surface, an inner surface orientedtoward the inner surface of the other body portion, a distal end wall,and a proximal end wall, each of said body portion further defining asupport surface extending along said inner surface of said body portionand along each of said first and extensions of said body portion, saidsupport surfaces facing away from one another in opposite directions andeach is configured to support and guide a cutting instrument along saidinner surface of said respective body portion and along said first andsecond extensions extending from said respective body portion.
 20. Theinstrument of claim 16, wherein said body portion of at least one ofsaid first and second spreading members includes a stepped regionextending from said actuator assembly, said stepped region spacing saidfirst and second extension members of said at least one of said firstand second spreading members from said first and second extensionmembers of the other of said first and second spreading members withsaid actuator assembly in an unactuated position to provide a minimumvertical spacing between said extensions of said body portions.